Abstract: OBJECTIVE To investigate the mechanism of balance transformation of Th17 and Treg by Kuijie Gailiang Prescription (KGP) and to investigate the role of KGP in the treatment of ulcerative colitis (UC) from the source of effector T cell activation Treg and Th17 cells. Deep-level mechanism of action and targets. METHODS The UC mouse model was induced by 3.5% DSS and randomly divided into normal group， model group， 5-ASA group and low and high dose KGP group， with 8 rats in each group. Observe the body mass， stool consistency and hemorrhage of each group， calculate the index of disease activity， observe the pathological changes of colon tissue by HE staining of colon tissue， and detect the levels of Treg and Th17 cells in mouse spleen by flow cytometry. RESULTS KGP had a therapeutic effect on UC mice. The disease activity index was significantly reduced (P<0.05)， and the pathological changes of colon tissue were improved. Compared with the normal group， the levels of CD4⁺CD25⁺Foxp3⁺ Treg， IL-10， Foxp3， and Smad3 were down-regulated， and the levels of CD3⁺CD4⁺IL-17A⁺Th17， IL-17A， RORγt， and STAT3 were up-regulated in the model group (P<0.01); after KGP treatment， The levels of CD4⁺CD25⁺Foxp3⁺ Treg， IL-10， Foxp3， and p-Smad3 were up-regulated， and the levels of CD3⁺CD4⁺IL-17A⁺Th17， IL-17A， RORγt， and p-STAT3 were decreased. There was a statistically significant difference compared with the model group (P<0.01). CONCLUSION KGP may play a role in the treatment of UC by regulating Treg/Th17 immune balance in UC mice.